If one of these - absolutely fascinating - but read the limitations - particularly it is only good for one family of powders and a limited set of BC's. Still useful, and an astounding example of a graphical representation of a set of insanely complex mathematical equations. Worth Studying.

** EDIT - Nov 24, 2020 **

The Speer exterior ballistics calculator mentioned in this thread works as long as you know the velocity. My brain cross-connected that with the Powley Computer and PSI Calculator which is an INTERIOR ballistics exercise - and only applies to IMR Powders. An interesting article is shown here:

https://www.shootingtimes.com/editor..._200901/100159
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